1. Field of the Invention
The present invention relates to a network station power adjustment apparatus and a power adjustment method thereof. More particularly, the network station power adjustment apparatus and the power adjustment method thereof of the present invention are adapted to optimize a base station down-link synchronization channel transmitting power.
2. Descriptions of the Related Art
In conventional network communication systems, a base station down-link synchronization channel is used for initial synchronization connection between a base station and mobile stations, and the base station down-link synchronization channel transmitting power determines the maximum communication range covered by the base station. Therefore, the base station down-link synchronization channel transmitting power has a direct influence on the quality of synchronization between the base station and the mobile stations.
Specifically, to speak in an intuitive way, a high base station down-link synchronization channel transmitting power means that the initial synchronization connection can be accomplished by the base station within a wide communication range. In other words, if the base station down-link synchronization channel transmitting power is adjusted to be high, then a high synchronization connection quality will be obtained between the base station and the mobile stations. The conventional practice is to set a ratio of the base station down-link synchronization channel transmitting power to the maximum transmitting power of the base station as a fixed value according to practical experiences.
However, if the base station down-link synchronization channel transmitting power is adjusted to be overhigh, then the maximum transmitting power of the base station will be indirectly reduced to cause a limitation on the data transmission bandwidth between the base station and the mobile stations and, moreover, the interferences between down-link synchronization channels of different base stations will be increased. On the other hand, if the base station down-link synchronization channel transmitting power is adjusted to be too low, then the communication range in which the base station can accomplish the initial synchronization connection will be narrowed.
Furthermore, when pseudo noise codes are used for synchronization between the base station and the mobile stations in a conventional Wideband Code Division Multiple Access (WCDMA) network system, the network system mainly utilizes a 3-stage cell search to accomplish the synchronization. Therefore, in case that the frequency errors of oscillators of the mobile stations and the base station down-link synchronization channel transmitting power are both high, then mobile stations having a high signal-to-noise ratio (i.e., closer to the base station) will unexpectedly have a longer synchronization time instead.
Accordingly, an urgent need exists in the art to provide a solution that can dynamically adjust transmitting powers of different channels of stations in a network system according to the network environment so that the aforesaid shortcomings of the prior art can be solved.